|
|
|
|
|
|
|
||
Original Article |
s.wray{at}liverpool.ac.uk
Moderate cooling of smooth muscle can modulate force production and may contribute to pathophysiological conditions, but the mechanisms underlying its effects are poorly understood. Interestingly, cooling increases force in rat ureter, but decreases it in guinea pigs. Therefore, this study used ureteric smooth muscle as a model system to elucidate the mechanisms of the effects of cooling on excitation-contraction coupling. Simultaneous recordings of force, intracellular [Ca2+], and electrical activity were made in intact ureter and ionic currents measured in isolated cells. The increase in force amplitude in rat ureter with cooling was found to be due to a significant increase in the duration of the Ca2+ transient. This in turn was due to a marked prolongation of the action potential. In guinea pigs, both these parameters were much less affected by cooling. Examination of membrane currents revealed that differences in ion channel contribution to the action potential underlie these differences. In particular, cooling potentiated Ca2+-activated Cl– currents, which are present in rat but not guinea pig ureteric smooth muscle, and prolonged the plateau of the action potential and Ca2+ entry. The force-Ca2+ relationship revealed that the increased duration of the Ca2+ transient was sufficient in the rat, but not in the guinea pig, to overcome kinetic lags produced in both species by cooling and potentiate force. Ca2+ entry and release processes were largely temperature-insensitive, but the rate of relaxation was very temperature-sensitive. Effects of cooling on myosin light chain phosphatase, confirmed in experiments using calyculin A, appear to be the predominant mechanisms affecting relaxation. Thus, smooth muscle is diverse in its response to temperature, even when experimental variables, such as the mode of stimulation, are removed. Although the biochemical and mechanical events accompanying contraction are likely to be affected in similar ways by temperature, differences in electrical events lead to subsequent differences in these processes between smooth muscles.
Key Words: force • electrical activity • ureter • E-C coupling • Ca-activated Cl channels
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Facebook 
Reddit 
Technorati 
Twitter What's this?
This article has been cited by other articles:
|
|
 |
|
  A. Y. Oo, A. R. Conant, M. R. Chester, W. C. Dihmis, and A. W.M. Simpson Temperature Changes Stimulate Contraction in the Human Radial Artery and Affect Response to Vasoconstrictors Ann. Thorac. Surg., January 1, 2007; 83(1): 126 - 132. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. C. Featherstone, M. G. Connell, D. G. Fernig, S. Wray, T. V. Burdyga, P. D. Losty, and E. C. Jesudason Airway Smooth Muscle Dysfunction Precedes Teratogenic Congenital Diaphragmatic Hernia and May Contribute to Hypoplastic Lung Morphogenesis Am. J. Respir. Cell Mol. Biol., November 1, 2006; 35(5): 571 - 578. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. C. Featherstone, E. C. Jesudason, M. G. Connell, D. G. Fernig, S. Wray, P. D. Losty, and T. V. Burdyga Spontaneous Propagating Calcium Waves Underpin Airway Peristalsis in Embryonic Rat Lung Am. J. Respir. Cell Mol. Biol., August 1, 2005; 33(2): 153 - 160. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y. Li, H.-D. Je, S. Malek, and K. G. Morgan Role of ERK1/2 in uterine contractility and preterm labor in rats Am J Physiol Regulatory Integrative Comp Physiol, August 1, 2004; 287(2): R328 - R335. [Abstract] [Full Text] [PDF]
|
|
|
|
